World's Fastest NXTien

We built this really fast NXT based vehicle over the weekend to see how far you can step up the rotations from a NXT motor before you reach the point where the power delivered to the wheel is no longer enough to make the vehicle move.

I would go for large thin wheels, rather than a track. Like a racing bike vs. a mountain bike, the amount of surface area you have in contact with the ground increases the friction, so you have to deliver more power to go at the same speed.